Telegraph system.



the count UNITED STATES PATENT OFFICE.

LOUIS A. ironrmnie, or new max, 1:. 1., AND scones c. commutes, or use. omen, NEW JERSEY, ASSIGHQBB 'ro fwns'rmm nwc'mm commmr, INGOBPOEA'I'EIQ, 01'

NEW YORK, u. 7., A coaroan'inon. or new YonK.

'TELEGBAPH arse-m1.

New York, in the county of New York,-

State of New York, and at East Orange," in of Essex, State of New Jersey, respective .y, have invented certain new and useful Improvements in Telegraph Systems, of which the following a full, clear, concise, and exact description.

This invention relates to telegraph systems and more particularly to systems for the simultaneous transmission of a plurality of messages over one and the same line circuit.

The object of this invention is a circuit arrangement whereby an additional alter nating current telegraph channel may be superimposed on a 'compositcd telephone line without introducing utual interference to control the application of higher frebetween the several clrannelsoiiv connnunication.

It is common practice in the telephone art to operate a direct current Morse telegraph channel over each wire of a telephone pair. Each oft-hose telegraph channels may furthermore be duplexed ,so that simultaneously with the use of a pair of wires for telephone purposes, four telegraph messages may be sent, two from each end of the line.

Such an arrangement requires special equipment for signaling the telephone SttttlOl'lS inasmucluus the usual 16 cycle ringing current would otherwise cause false signalsin the Morse instruments. Consequently, the usual low frequency ringing current is made quency ringing current (usually about 135 cycles) to the line, which in turn: at'the receiving end of the line operates arelay to connect the. 16 cycle current to the local signaling apparatus.

In applying an additional alternating current telegraph clitinhel to; such a system a current ne e n'pyihiaa circuit arrangeleas't 'lijkelihobd joi tfittlrbance with, or disturbance fronlrth"othefifichannels of (T0111- municliti." T I This inventon, thplfe'forc provides a pair of transfori'ners'," out of which has a winding in series with the main line conductor Specification of Letters Patent.

Patented Dec. 9, 1919.

Application filed May 28, '1 91 8. Serial R0. 287,045.

and the other of which has a winding in series with the artificial line branch of the duplex network. Bridged between the mid-points of these windings is a. receivin circuit for the alternating current telegrap signals lWlliCll contains inductance and capacity so chosenin value as to make the reqeiving circuit roughly resonant to the frelpiency of the alternating current -tele graph signals. The receiving circuit is linked inductively ith the receivin apparatus proper which consists of a series of amplifiers and filtering circuits leading to the signal indicating device, the filtering circuits being chosen to admit the passage of the alternatin current telegraphic frequencies (prefera ly about cycles) and to exclude other frequencies such as the composite ringing frequency, the telephonic frequencies and the lower frequency"Moi-se thumps frornthe direct current .duplex.

Each of the transformers above men-' tioned is equipped with a transmitting winding, the two being connected in series with an alternating current source and a transmitting key. Each of the two transformers is furthermore provided with a third winding connected one with the other to form a closed circuitlinking the main line with the artificial line and serving to lessen danger of interference between the direct current duplex and the alternating current telegraph channel.

In the drawing, Figure 1, there is shown an equipment suitable for the transmission and reception of telegraphic impulses by means of direct currents and also equip,- ment for the transmission and reception of telegraphic signals by. means of alternat ing currents, while in Fig. 2 there are shown in plan form twp metallic telephone cir cuits arranged ina manner suitable for carrying out $1 service features of this in; vention. 1 i In describing this system it will first pointed out that the equipment shown Fig. 1 may he understood typical of four telegraphic eqnipmentsiridicated by the rei crencf b'haracters 1, 2, 3 and 4 in Fig. 2 of-l than raw ing. these equipments being orringed toioperate from earth ov'er res ectn've' line conductors 5. 6, 'i and 8 which or n a. first and a. second telephone line circuit respectively indicated by the referenom chercurrent portion of armature of which controls actors A and B. As shown in the drawing, a first telephonic equipment provides for operation over the conductors 5 and 6 ot the circuit A, a second telephonic equipment may be provided for o crating over theeondoctors 7 and 8 of tie circuit B, while a third telephonic equipment may be employed to o crate in superposed or so-called hantom re ation over the two physical cirquits A and B. By means of t 11s arrangement it results that during the time the sevoral telephone equipments are in use the several direct current telegraphic channels and the several alternating current telegrupl'nc channels may also be in operation. I

' In more specifically describing tlns system, attention will now be directed to Fig. 1 of the drawing. In considering the direct the telegraphic equipmcnt a transmitting means 10 may be operated to selectivel control associated sources of grounded line current indicated by thc conventional plus and minus signs at tlus transmitter. Such currents after travcrsing the windings of an impedance coil 11 reach the apex or neutral point of a duplex equipment formed by ratio arms 12 and 13. The currents divide at this point over a must atn which may be traced through the diferentially connected windings 16 and 17 of a transformer 15, thence through a condoctor 20 and an impedance coil 21 (Fig. 2) to, say, the line conductor 5 of. .he circuit A. The second path extends through the bridge arm 13, the differentially con nected windings 26 owner and 27 of a trans 25, thence through the windings ofan impedance unit'39 and the capacity and resist ance aths of an artificial line 30 to earth. As well understood in connection with duplex circuits, such outgoing currents transmitted by the key 10, although neutralized and non-effective with respect -to a recciv ing relay 31, may traverse the lead 2Q and the line conductor 5 to actuate a receiving relay in a similar duplex equipment at a distant station. In a converse manner, direct current impluses originating at'a distant station may arrive over the line conductor 5 (Fig. 2), pass-through the impedance coil 21,- thence by way of the-lead ill, the windings 17 and 16 of the transformer 15 (Fig. 1), to actuate the receiving relay 31, the contacts in the circuit of a receiving equipment not shown. For transn'iitting telegraphic signals by means of alternating currents, at transmit ting key 40, when depressed. closes contacts 41 to connect a source 42 of alternating currents, preferably of sine-ware forunthrough the windings 18 and 28 of the transformers l5 and 25 respectively to ground. In addition to closinr the contacts 41 such operation of the toy 4U separates contacts 43, thereby opening a normally closed loop circuit which includes the windings 19 and 2!) of the transformers l3 and 25 rcs u-ctircly. The purpose of this loop circuit will presently appear. Alternating currents in the transformer windings l8 and :48 cause corresponding current changes in the windings 17 and 27 of the transformers l3 and 2.: respectively. ()ne tcrmjuatol the winding 17 is connected through a comlcnscr 32 am the winding 36 of a transformer 1-53 to carth. while the other terminal of the winding 17 iii-connected by the lead 20 and thc iuduc tance coil 21 (Fig. 2) to thc linc conductor 5 at the distant end of which is a suilahle receiving equipment presently to be described.

At the transformer :45 currentsinduced from the winding 28 arc manifested in the winding 27 which is conncctcd to permit such induced currcnls to circulate in a closed loop formed through a first grounded condenser ti l, a sccond condenser ill and a winding it? of the transformer it? to curth. Since the line portion of the transmitted alternating currents which trurcrsc the winding 30 of the transformer 2-5:) are counlcractiul by the artificial linc portion of the alternating currents which traverse the winding 37 of this transforuu-r, m-utralixation is established in the transformer 35 and u receiving system connected to the winding 38 of this transformer is therefore not affected by such transmitted alternating currents.

In the reception of messages transmitted from a distant station alternating currents may arrive over the line conductor 5 (Fig. 2), pass through the impedance coil 21, the conductor 20. winding 17 (Fig. l) of the transformer 15, thence by way of the condenser 32 and winding 36 of the transformer 35 toearth. Such incoming currents through the winding 36 set up corresponding currents in the winding 38 of the transformer 35 and since the latter winding is connected to form a closed loop. through a current amplifier magnet 45 such current changes will in turn establish like current effects in a microphone pile -ll which may be similar to a transmitter button.

Variations of current potential from a source 47, as set up by the microphone 46, act through a transfori'ner 48 to operate a second amplifier which comprises operating coil 49 andmicrophone pile 50. In turn the microphone 50 causes current changes from a source 51 which may, through a transformer 52, become elfective in a network or filter system comprising transformers 53 and 54 and respectively associated eondensers fifi and 56. polarized relay 57 connected to the secondary windings of the transformer 54 is arranged to normally connect battery through the winding of a relay 58 and an impedance unit 59 to earth. For con rcniencc. the armature of the polar relay 57 may be biased by means of a retractile spring as shown to normally retain the circuit just traced thrbu h the relay 58. The relay 58 being normafiy energized, connects an associated source of positively poled current through the winding of a=polar relay 60 in of this relay to release and connect a source of negatively poled--currei1t through the polar relay 60 in substitution of ThOPOfiitlVG current already described. Although each positive half-wave or impulse through the relay 57 may bias the armature of this rela y to close the circuit through the relay 58,

the operating time constant of the relay 58 with respect to the frequency of the received alternating currents is such that this relay is practically deiinergiaed during the presence of incoming alternating currents, thereby maintaining negative bias of the relay (it? in retaining the device 61 operated.

From this description of the manner in which incoming alternating currents are re ceived, it will be clear that relatively feeble currents from the line circuit will receive a first and second amplification, following which they willpass through the filtering network to arrivein the form of currents which more nearly resemble the form of the alternating currents impressed on the line conductor at the d istunt station, thereby insuring reliable and proper operation of the receiving devices to be controlled.

The windings l9 and 29 on the transformers 15 and 25 are used for the purpose of compensating for unbalance in the direct current duplex system. The circuit through these windings is normally closed by the backcontuct 43 of the key 40 and forms an inductive coupling between the line side and the artificial line side of the duplex network. If, for example, there is a momentary imbalance causing more current to pass from the transmitting key 10 to line 20 than to the artificial line 30, there 'will be a trans 'fer of current from the Winding 19 to the winding 29 to compensate for this unbalance. The alternating current receiving system is therefore less liable to disturbance from such unbalance than if the inductive coupling were not used.

The condensers 66 and 67 are bridged around the ratio arms 12 and 13 to absorb any inductive kicks caused by the operation of the transmitting hey if), while a third mndenser 68 is bridged across the terminate of the relay 31 th proridr a path for the alternatin current signals and to prevent such signa s from interfering with the operation of the said relay.

Referring to Fig. 2 of the drawing, a path for telephonic currents over the first circuit A may be traced from the line conductor 5 through condenser 70, the Windings 72 of a transformer 71, a condenser 74, thence returning to the distant'station over the second line conductor 6 of this circuit. Such currents in the winding 72 of the transformer 71 setup corresponding currents in the winding 73 to act over a circuit one side of which is formed through the contacts 81 of a relay 80, a conductor 85, the contacts 86 of a relay 90 to the tip contact member 92 of a telephone jack 91; the other side of the circuit consists of the contacts 82 of the relay 80, a conductor 95, the contacts 87 of the relay 90 to a ring contact member 93 of the jack 91. As well understood in the art, telephonic devices (not shown) may be included with the jack 91 for communicating by way of the paths alre-ruly traced oiei' the circuit A. in order that call-signals may be operated over the line circuit in connection with the telephonic traffic without such call-signals interfering with either the direct current or the alternating current telegraphic service, the devices shown intermediate the transformer winding 73 and the telephone jack 91 are provided and will now be described.

In initiating a telephone call-signal byway of the jack 91 of the circuit A, it will be understood that equipment, not shown, but included with this jack is provided for applying an alternating 'current of reluti'vely low frequency, as, say, approximately 16 cycles per second to the contact members 92 and 93. Such connection with the jack 9] separates its normal contacts to dis-con nect a signal receiving device 94 which, for convenience, is shown in the form of a drop. The low frequency alternating, current may traverse the contacts 86 of the relay 90, the conductor 85, a condenser 100, the windings of a polarized relay 101 to the conductor 95, thence returning over the contacts 87 of the relay 90 to the opposite side of the connection at the jack 91. The armature of the relay 101 is so arranged that its contacts 102 and 103 are normally open. lmler the action of alternating currents through this relay its armature will be reriprorntcd in phase therewith to alternately,

close the contacts 102 and 103. When the contacts 102 close, a source of grounded battery 10 1 will be connected through these confacts and associated resistances with a bus conductor 105. From this bus conductor the circuit divides over one path formedthrough an alternating current relay 106 and abat- Ker iii? to earth and over another path which includes the winding of a second altacts S3 and 84 this relax ternating current relay 10S and a battery 10'.) to earth. \Vhile the battery 104 connected to act in differential relation with respect to the batteries 107 and 109, the potential of the. battery 10- is greater than the potential of the batteries 10? and 109. Ordinarily. a relation in which'the potential of the battery 104 is twice the potential of either of the other batteries, has been found to give satisfactory results. During the time the contacts 102 are closed it will therefore be clear that current may flow from the battery 1th over the circuits traced through each of the alternating current relays 106 and 108, and conversely current in an opposite direction will 110w from the hat-- teries 107 and 108 through the respective alternating current relays to earth during instants the contacts 103 of the relay 101 may he closed. In this manner it. will he clear that alternating current effects may be active through the relays 101' and 103 during the time alternating currents may be applied by way of the jack $11, as described. and 'it will further he clear that the frequency of the alternating currents through these relays will he in phase with the alternating currents applied at the jack. The relay 106 is of such design or adjustment that it will not be affected hy the low frequency alternating urrents, the relay 108, however. is so proportioned or adjusted as to readily respond to the low frequency currents described. Operation of the relay 108 completes a circuitfrom a source of current 100 through the winding of'a relay 110 to earth. Operation of the relay 110 completes a circuit from an associated battery which extends through the windings of a relay 111 and the relay 80 to earth. Relay 111 thereby operated completes a loop circuit which includes an alternating current generator 112 and a winding 114 of a transformer 1.13. Operation of the relay 80 causes separation of its contacts 81 and 82 to disconnect the conductors 5-13 and 0 and in closing its coni-onnccts a secondary winding 115 oi the transformer 113 in a closed loop circuit which includes the winding 73 of the transformer T1. The frequency of the current produced by l'he generator 112 is relatively high. say. approximately 133 cycles per Second. and such currents ma traverse the line conductors 5 and G of the metallic circuit A to reach a distant station and there operate a telephone call signal which may he typical of the signal 01 shown at the present station.

In describing operations whereby a telt phone call-signal originating at a distant station may he received at the present station, let it be assumed that at the distant point operations are carried out in a manner similar to that just described in connection with the sending out of high frequency signaling currents from the present equipment. Such incoming alternating currents act through the transformer T1 to complete circuit over the contacts 81 and H2 of the molar) H0, thence hy way of the conductors 85 and 0.7 through the condenser 100 and relay 101. The relay 101 is so constructed or ad usted that it may readily respond to alternating currents of either low or high frequency, therefore, in responding to the high frequency currents the contacts 102 and 103 of this relay are alternately closedin phase therewith to establish alternating current effects of a corresponding frequency over the operating circuits already traced through the relays 100 and 10s, In this case, the low frequency relay 105 will continue inert while the high frequency relay 1015 will close its contacts to complete a circuit from a battery 110 to operate a relay 117. The operation of the latter relay connects a hattery 110 to operate the relay 00 and separation of the contacts 81' and 87 of the latter relay disconnects the conductors H5 and 05 from the jack 01, while closure of the contacts 88 and H9 of this relay connects a low frequency generator 118 to act over the normal contacts of the jack 01 in operating the drop signal 04. it hcing understood, of course, that no comicction would he present in the jack 91 during times it may be necessary to receive a call signal. as described. from a distant station.

The various telephonic equipments, directcurrcnt telegraphic equipments. and alternating current telegraphic equipments are so arranged and proportioned. one equipment with another. that the various callsignal control and telephonic operations described may he carried on without interfering'onesignaling method with another even when a telephone equipment. similar to that shown and described in connection with the circuit A, is included with the transformer T1 for carrying out telephonic service in connection with the physical circuit B. while similar equipment may be connected to the conductors 06 and 97 for telephone service over the phantom circuit formed jointly over the circuits A and B as shown.

The condensers T coils 76 and T7 serve to allsol'l) or prevent other than telephonic currents reaching the telephonic equipment just described. a

5 and '58 and impedance ground connection estahlished interinediate- 120 in the telephqne "rentsthroug the tele Iii-the working of t circuit already mentioned,

portion of the equipments revent loss of telephonic curraphic devices,

e phantom telephone telephonic and call-signal current paths may be traced by Wayfof the conductorllfi to a neutral or simplex point on the coil 72 of the transformer 71, from which oint the currents may di an .a s to vide equally in differential relation over the tion may act through the phantom circuits 'ust traced and.be manifested on telephonic evice assumed as connected to the conduc-' tors 96 and 97.;

In addition to, its being understood that similar telephonic equipment may be present stations.

at a distant station -of the physical out departing invention.

for each one of the three telgphone channels described, it will also be un erstood that telegraphic equipments corresponding with the equipments 1, 2, 3 and i may also be present at a distant station or -In further increasing the service capacity circuits A and B telegraphic equipments of the direct current and alternatin current types as already described may connected to operate in earth return relation-over the leads 96 and 97 as simplexed over the two physical circuits, respectively.

A though the arrangement chosen for illustrating this invention is considered to representa referred embodiment thereof, it will be un ers'tood that changes in the arran ent of the eguipmnt may be made rom the spirit of this What is claimed is: 1. The combination with a line conductor and a direct current duplex telegraph systcm connected thereto having an artificial line two ratio arms and a receiving circuit bri 'ng said ratio arms and connecting said line conductor with said artificial line, of a receiving circuit for alternating cur-.

relit signals bridged between said line conductor and said artificial line, and a comcoupling between said line conuctor and said artificial line.

2. A system for signaling'by currents comprising a real line,

alternating an artificial line, a transformer having a winding in series with said real line, a second transformer having a winding in series with said artificial line, a receiving circuit connecting the mid-points of said windings, transmitting windings on said transformers, and a source of alternating current and a transmitting key in circuit with said transmitting windings.

3. A system for signaling by alternating currents comprising a real line, an artificial line, a transformer having a winding in sethe mid-points of sai windings, and a re:

ceiving device inductively connected to said bridge circuit.

5.A system for signaling by alternating currents comprising a line conductor, an artificial line, a transformer having a winding in series with said line conductor, a second transformer having a winding in series with said artificial line, a receiving circuit connecting the mid-points of said windings, transmitting windings on each of said transformers, a normally closed circuit including a third winding on each of said transform,- ers, a source of alternating current, and means for simultaneously supplying current from said source to said transmitting windings and for opening said normally closed circuit.

.,6. A signaling system comprising a real line, an artificial line, a transformer having.

a winding in series with said real line, a. second transformer having a winding in series with said artificial line, a circuit containing inductance and capacity connecting the mid-points of said windings, and a signaling indicating device inductively'connected to said circuit.

7. The combination with a direct current duplex telegraph system comprising a line conductor and an artificial line, means for signaling by alternating currents over said line conduct/or, simultaneoifily with the operation of said direct current system, comprising a transformer having a winding in series with said line conductor, a second transformer having a winding in series with said artificial line, a bridge circuit containing a direct current receiving relay connecting a terminal of one of said windings ing the mid-points of said windings and an alternating current signal'recciving device inductively connected to said second bridge circuit.

8. The combination with a direct current duplex telegraph system comprisinga line conductor and an artificial line, of means for signaling by alternating currents over said line conductor simultaneously with the operation of said direct current system comprising a transformer having a winding in series with said line conductor, a second transformer having a winding in series with said artificial line, an alternating current receiving circuit connecting the midpoiuts of said windings, a transmitting winding on each of said transformers. and a source of alternating current. and a transmitting key in circuit with said transmitting windings.

E). The combination with a telephone line conductor and a bridge duplex telegraph equipment connected thereto and cornprising two ratio arms and an artificial line. of a direct. current signal receiving circuit and an alternating current signal receiving circuit both bridged between said line con due-tor and said artificial line. and an indu tive. coupling between said line conductor and said artificial line.

10. The combination with a telephone line wnductor of auxiliary means for signaling over said conductor by alternating currents comprising a transformer having a winding in series with said dine conductor, an artificial line, a second transformer having a winding in series with said artifical line, a circuit bridged between the mid-points of said transformers and resonant at the fre quency of said auxiliary signals. a signal receiving device and a selective circuit connecting said receiving device with said receiving circuit and arranged to exclude tele phonic frequencies from said receiving de-' vice.

11. In combination. with a line conductor, an artificial line. a circuit containing 'apacity connecting said line ciiruit with said artificial line, a transformer having a winding in series with said line circuit, a second transformer having a winding in series with said artificial line a brid e circuit contain-i 

